Date: Sun Jul 12 11:33:20 2020 Errors in Heat of Formation

Errors in Calculated Heats of Interaction in Kcal/mol for Dimers of Water set

(Home Accuracy Manual)

Empirical

Name

Expt.

PM7

PM6-D3H4

PM6-D3H4X

PM6

PM6-DH2X

PM6-DH+

H4O2 Water dimer Structure 1 (Non-planar open Cs)

-5.00

0.11

-0.22

-0.22

1.04

0.06

-1.54

H4O2 Water dimer Structure 2 (Open Ci)

0.52

0.31

0.22

0.22

0.31

0.38

0.79

H4O2 Water dimer Structure 3 (Planar Open Cs)

0.57

0.57

-0.04

-0.04

0.09

0.49

1.95

H4O2 Water dimer Structure 4 (Cyclic Ci)

0.70

0.36

0.53

0.53

-0.41

0.11

1.82

H4O2 Water dimer Structure 5 (Cyclic C2)

0.95

0.72

0.76

0.76

-0.18

0.41

2.13

H4O2 Water dimer Structure 6 (Cyclic C2h)

0.99

0.73

0.51

0.51

-0.40

0.46

2.02

H4O2 Water dimer Structure 7 (Triply Hydrogen Bonded

1.81

-0.29

0.34

0.34

-0.88

-0.28

1.40

H4O2 Water dimer Structure 8 (Non-planar Bifurcated

3.57

-0.02

0.25

0.25

-0.90

-0.18

1.45

H4O2 Water dimer Structure 9 (Non-planar Bifurcated

1.79

-0.63

0.11

0.11

-1.06

-0.65

0.94

H4O2 Water dimer Structure 10 (Planar Bifurcated C2v

2.71

-0.80

-0.18

-0.18

-1.29

-0.72

0.96


Source of the reference data: Tschumper, G. S., et al. (2002). "Anchoring the water dimer potential energy surface with explicitly correlated computations and focal point analyses." The Journal of chemical physics 116(2): 690-701.

The lowest-energy conformation of the water dimer is Structure 1. This is 5.0 Kcal/mol more stable than the two separate water molecules.

The energies of the other conformers, Structures 2-10, are all relative to Structure 1.